Roy Hodgson has admitted being concerned about Wayne Rooney's frame of mind approaching a World Cup season for England and intends to call together the Manchester United and Chelsea players in his squad to insist they do not allow club issues, in this case the future of his principal striker, to impinge on the national team.

With half the outfield players in Hodgson's 25-man party to face Scotland next week coming from Old Trafford and Stamford Bridge, the England manager is worried Rooney's proposed move to Chelsea will not only be on the striker's mind but also involve other members of his squad.

Hodgson is particularly aware of the relationship between Rooney and Ashley Cole and does not want the pair to be colluding about the striker's possible move to Chelsea. "I do accept a duty of care," he said. "We're not naive. Ashley Cole and Wayne are quite close friends. David Moyes must know that as well. If they weren't speaking in a hotel, they would be speaking on the telephone.

"I will try to make it clear to everybody, the Chelsea players and the Manchester United players and anyone else for that matter, that this is England. As far as we're concerned, you can speak as much as you like to each other now but during these two or three days this is England, this is England against Scotland and, even more importantly, the matches beyond Scotland.

"I don't expect anybody for one minute to fracture their concentration from what's important. If he [Rooney] does take some part in the game I would expect him to put any personal problems he may have, or any professional concerns he might have, behind him and give everything for England."

Rooney has not started a game since 28 April and Hodgson is concerned about the effect a tumultuous few months might have had on a player who trained with United's reserves on Thursday and is threatening to hand in a transfer request, citing long-standing unhappiness at the club.

"You cannot divorce the way a person feels from the way he plays," Hodgson said. "We sometimes forget that. We expect players always to play at the level that is expected of them, irrespective of their mental state. We want to dismiss that – but we can't."

As well as taking a calculated gamble on Rooney's fitness, Hodgson has brought Rickie Lambert of Southampton into his first England squad, at the age of 31, to provide back-up in the absence of Daniel Sturridge and Andy Carroll.

"At the moment we are not blessed with enormous choice when it comes to forwards," Hodgson said. "We can't get away from that, can we?

"Every time I've sat down [at press conferences] we've discussed the paucity of competition at forward level, especially as many times during that 16 months we've had injuries. We haven't had an awful lot of choice. But it would be harsh if you then turn that against Rickie Lambert. He's a very good technician, good in the air, his understanding of the game is good and he's scored goals. You could argue: what more criteria do you want when you are selecting a forward? I make no apologies for his selection."

Hodgson wants to play a strong team but is aware that Arsenal will be unhappy if Jack Wilshere plays the full match, as well as being mindful that Frank Lampard and Jermain Defoe are returning from injury. Wilfried Zaha has been promoted to the senior squad and Hodgson appears untroubled by the feedback within the Football Association about the former Crystal Palace man being one of the players whose attitude was poor during the Under-21 European Championship.

"It's very dangerous to start taking other people's judgments," he said. "It would be wrong of me to say I'm going to hold something against a player when I haven't actually been there myself.

"The same applies to Jonjo Shelvey. I worked with Shelvey [at Liverpool]. He was fine with me at Liverpool and when I watched him play for Swansea against Malmo he played very well. As far as I'm concerned, I pick a player. If it turns out when I work with him that he doesn't have a good attitude or doesn't do well, I will make the call then."